Temporal changes in the bacterial microbiome of the salivary gland and midgut tissues of Rhipicephalus sanguineus (s.l.) ticks in South Africa

Abstract

Tick-borne bacterial pathogens from animals play a significant role in the (re)emergence of human diseases. Rhipicephalus sanguineus sensu lato, a globally prevalent tick, predominantly parasitises domestic dogs but can also feed on humans. We characterised temporal changes in the bacterial microbiome of the midgut and salivary gland tissues of R. sanguineus s.l. ticks and analysed their potential as reservoirs for pathogenic bacteria. A 16 S microbiome and amplicon sequence variant (ASV) approach was used to study the bacteria present in the tissues of R. sanguineus s.l. ticks collected from dogs in Hluvukani, a village in a rural community in Bushbuckridge, Mpumalanga, South Africa, in 2016, 2017 and 2019. Post processing, we obtained 43,161 total sequence reads which were clustered into ASVs by sample year. The final ASVs dataset consisted of seven genera: Coxiella, Anaplasma, Escherichia/Shigella, Ehrlichia, Borrelia, Rickettsia and Wolbachia. No differences in the microbiome profiles of the MG and SG tissues were noted. Coxiella endosymbionts dominated the microbiome in all years. Anaplasma was first detected in 2017, and an increase in Anaplasma levels was detected in 2019, when compared to 2017. All other genera were present at low levels. With the exclusion of Wolbachia, the other detected genera could have pathogenic potential, highlighting the role that R. sanguineus s.l. might play as a reservoir of pathogens.